1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 2 3<html> 4 5<head> 6<title>iget<kind></title> 7<link rel=stylesheet href="opcode.css"> 8</head> 9 10<body> 11 12<h1>iget<kind></h1> 13 14<h2>Purpose</h2> 15 16<p> 17Perform the identified object instance field operation with the identified 18field, loading or storing into the value register. 19</p> 20<p> 21Note: These opcodes are reasonable candidates for static linking, altering the 22field argument to be a more direct offset. 23</p> 24 25<h2>Details</h2> 26 27<table class="instruc"> 28<thead> 29<tr> 30 <th>Op & Format</th> 31 <th>Mnemonic / Syntax</th> 32 <th>Arguments</th> 33</tr> 34</thead> 35<tbody> 36<tr> 37 <td>52..58 22c</td> 38 <td>i<i>instanceop</i> vA, vB, field@CCCC<br/> 39 52: iget<br/> 40 53: iget-wide<br/> 41 54: iget-object<br/> 42 55: iget-boolean<br/> 43 56: iget-byte<br/> 44 57: iget-char<br/> 45 58: iget-short<br/> 46 </td> 47 <td><code>A:</code> dest value register or pair; (4 bits)<br/> 48 <code>B:</code> object register (4 bits)<br/> 49 <code>C:</code> instance field reference index (16 bits)</td> 50</tr> 51</tbody> 52</table> 53 54<h2>Constraints</h2> 55 56<ul> 57 <li> 58 A and B must be valid register indices in the current stackframe. 59 </li> 60 <li> 61 For the -wide variant, also A+1 must be a valid register index in the 62 current stackframe. 63 </li> 64 <li> 65 Register vB must contain an object reference. 66 </li> 67 <li> 68 C must be a valid index into the field reference pool. 69 </li> 70 <li> 71 The field must be an instance field. The type of the field denoted by C must 72 match the variant of the instruction. 73 </li> 74</ul> 75 76<h2>Behavior</h2> 77 78<ul> 79 <li> 80 The value of the given instance field is read from the given object and 81 moved into the given register vA, that is, vA'=<object>.<field>. 82 </li> 83 <li> 84 If v(A-1) is the lower half of a register pair, v(A-1)' becomes undefined. 85 </li> 86 <li>For all but the -wide variant, if v(A+1) is the upper half of a register 87 pair, v(A+1)' becomes undefined. 88 </li> 89 <li> 90 For the -wide variant, if v(A+2) is the upper half of a register pair, 91 v(A+2)' becomes undefined. 92 </li> 93</ul> 94 95<h2>Exceptions</h2> 96 97<ul> 98 <li> 99 NullPointerException if object is null. 100 </li> 101 <li> 102 IllegalAccessException if <object>.<field> is not visible from 103 the current context according to the usual visibility and access rules of 104 the Java programming language. 105 </li> 106</ul> 107 108</body> 109</html> 110